Conformal cooling is the highest-ROI application of DMLS tool steel printing. The concept is simple: cooling channels that follow the cavity surface at constant distance, versus the straight channels drilled in conventional tooling that run point-to-point regardless of cavity geometry.
Thermal Physics of Conformal Cooling
Heat must be removed from the plastic part to complete solidification before ejection. In conventional tooling, the nearest straight drilled channel may be 20–40 mm from complex curved features. In conformal tooling, the distance is typically 3–6 mm — constant across the entire cavity. Reduced distance reduces thermal resistance and enables faster heat extraction at the same coolant flow rate.
Measured Results
| Application | Conventional Cycle | Conformal Cycle | Reduction |
|---|---|---|---|
| ABS housing (1.5 mm wall) | 38 s | 23 s | 39% |
| PP living hinge (0.8 mm) | 22 s | 15 s | 32% |
| PC lens (3 mm thick) | 65 s | 42 s | 35% |
| POM gear | 28 s | 19 s | 32% |
H13 Design Rules for DMLS
Channel diameter: Minimum 2 mm (smaller clogs). Maximum 8 mm for standard inserts. Wall thickness to channel: Minimum 3 mm from channel centerline to mold surface. Channel layout: Continuous serpentine preferred over branching (prevents short-circuit flow). Pitch-to-diameter ratio: 3–4D center-to-center spacing balances cooling uniformity with stress. Surface finish: EDM and electropolish cavity surface after DMLS; channel internal finish acceptable at as-built Ra 4–8 µm.
ROI Calculation
At 100,000-part annual volume, a 35% cycle time reduction = 35% more capacity from existing machines = significant avoided capital investment. DMLS insert premium ($3,000– $15,000 versus machined) typically pays back in < 6 months of production.